Numerous food products, and especially confectioneries, such as ice cream novelties and the like, are formed in a semi-fluid state and must be completely frozen prior to packaging and shipment. Freezing systems for such products include a conveying mechanism for the product having entry and exit positions, with the product normally being formed along the entry portion of the conveyor and removed at the exit portion of the conveyor. The main portion of the conveyor is located within a freezer box which is maintained at a sub-freezing temperature for the product.
Numerous cooling mechanisms may be employed for maintaining the temperature within the freezer box. One such mechanism involves the positioning of refrigeration coils along one upper side portion of the freezer box and positioning a plurality of fans on the opposite upper side portion of the freezer box, creating air flow generally perpendicular to the direction of travel of the conveying system through the freezer box.
A common problem with freezer systems is frost buildup. As frost builds on the cooling coils and other parts of the system, the freezer becomes less efficient, requiring down time for defrosting.
A system for reducing frosting of freezer boxes is disclosed in U.S. Pat. No. 3,857,252, the disclosure of which is hereby incorporated by reference. In this patent, the freezer box is divided into a large main chamber and a small chamber by a bulk head, or wall, separating the two portions of the box. The conveyor system passes through this small chamber through openings in the outer wall of the freezer box and the bulk head wall. According to the patent, the warm air which is drawn into the freezer box with the product at the entry portion of the conveyor will be dehydrated or defrosted within this small chamber, producing a snow-like effect within the small chamber, but leaving the main chamber basically frost-free.
Although this system is an improvement over prior freezer systems, there remains the possibility of warm air, or at least frost from warm air escaping the small chamber carried by the entry conveyor, entering the main chamber. This is due to the fact that by necessity there is a negative pressure at the opening of the freezer box where the conveyor enters the freezer box and the ability of the conveyor to thereby draw warm air along itself.
It is thus the primary objective of the present invention to isolate the conveying portion of the freezer system from the defrosting portion of the freezer system, providing a freezer system with improved efficiency.